Algae's powerful future: our oil addiction may be cured by one of the primordial sources of petroleum itself.

First, the bad news. A 2006 report by the U.S. Department of Energy (DOE) predicts that cars and trucks powered by batteries or hydrogen fuel cells will total only one-tenth of one percent of new vehicle sales in the year 2030, mainly because of the limited driving range, high vehicle costs, and

With fuel cells, there's also the problem of developing a cheap, abundant source of hydrogen to power them.

Under current policies, the DOE now predicts that relatively clean-burning ethanol and biodiesel won't supply more than 11% of the fuel for America's motor vehicles in the year 2030. Conventional crops can't produce enough of these biofuels per acre to meet the enormous demand, which is expected to grow 40% by then.

The numbers are daunting, but one solution to our growing hunger for transportation fuels may be very simple: algae.

Lowly, single-celled microalgae may eventually be used to make large quantities of biodiesel, ethanol, and even hydrogen. At a small DOE plant in New Mexico, researchers produced up to 50 grams of algae per square meter per day, using native algae species that naturally took over the ponds. This might be enough to yield 6,800 gallons of oil per acre if sustained for a year. That's 11 time more than any other biodiesel crop, including palm oil. The potential of algae-based biofuels has been covered by CNN, MSNBC, New Scientist, Technology Review, and dozens of other sources. But the unique challenges--and opportunities--of algae power are often left out of the discussion.

Today, the capital costs of establishing an acre of algae ponds (mixed by motorized paddle wheels) are still much higher than those for conventional oil crops producing biodiesel or for corn crops producing ethanol. But algae ponds require only a fraction of the land area. That's a critical advantage at a time when widespread biofuel production bears part of the blame for tropical deforestation and food shortages in developing countries.

Biodiesel from algae is lead-free, almost sulfur-free, biodegradable, and can run any modern diesel engine. Biodiesel also lessens global warming because it's made from plants that absorb carbon dioxide while they're growing, thus compensating for the carbon dioxide released when the fuel is burned. According to the DOE, unblended (B100) biodiesel fuel emits an average of two-thirds less [CO.sub.2] and five other air pollutants than does petroleum diesel. However, biodiesel is more likely to cause engine problems in cold winter weather unless it's blended with petroleum diesel. And burning biodiesel produces slightly more nitrogen oxide, although the amount of this air pollutant is much less when using biodiesel blends or the emission-control systems in new diesel vehicles.